Flash is extremely laggy on Firefox

(I'm not very good at English, if you don't understand something of my problem description please tell me)
I just decided to give another chance to Firefox and move from Google Chrome and this time I found that Nightly (version 18 for the time of this question / out of using Firefox, Firefox Beta and also Aurora), worked with a really good performance and support for complements and to be really fast on my daily stuff, my only problem is that once I tried watching videos on YouTube or doing any other kind of stuff that required Adobe Flash Player (version 11.4 at the time of this question) it just freezes, the browser gets really laggy and Nightly starts to eat about 70% or more of my CPU, throught it doesn't crashes and it's just painfully slow until I can close the page with some luck.
Now, I wanna start by clarifying that this happens to me in all the browser iterations like Firefox (15), Firefox Beta (16) and Aurora (17), not just in Nightly (18).
By the other side in Chrome (version 22 for the time of this question) this never happens to me, the videos are pretty fast and the performance is fine.
Also this problems just appears to happen when I'm using it on the page. If I put a video on fullscreen it goes plain smooth (even better than with Chrome), but once I get off fullscreen the lagg starts again.
I recently updated Flash to try to solve this and also reinstalled Flash, non of this worked out and I don't know that else could I do.
Also wanted to add that I'm using Windows 8 (Release Preview) and my PC runs on x64, since Firefox runs on x86 maybe this could have something to do, but I'm not sure.
Thanks.

(I'm not very good at English, if you don't understand something of my problem description please tell me)
I just decided to give another chance to Firefox and move from Google Chrome and this time I found that Nightly (version 18 for the time of this question / out of using Firefox, Firefox Beta and also Aurora), worked with a really good performance and support for complements and to be really fast on my daily stuff, my only problem is that once I tried watching videos on YouTube or doing any other kind of stuff that required Adobe Flash Player (version 11.4 at the time of this question) it just freezes, the browser gets really laggy and Nightly starts to eat about 70% or more of my CPU, throught it doesn't crashes and it's just painfully slow until I can close the page with some luck.
Now, I wanna start by clarifying that this happens to me in all the browser iterations like Firefox (15), Firefox Beta (16) and Aurora (17), not just in Nightly (18).
By the other side in Chrome (version 22 for the time of this question) this never happens to me, the videos are pretty fast and the performance is fine.
Also this problems just appears to happen when I'm using it on the page. If I put a video on fullscreen it goes plain smooth (even better than with Chrome), but once I get off fullscreen the lagg starts again.
I recently updated Flash to try to solve this and also reinstalled Flash, non of this worked out and I don't know that else could I do.
Also wanted to add that I'm using Windows 8 (Release Preview) and my PC runs on x64, since Firefox runs on x86 maybe this could have something to do, but I'm not sure.
Thanks.

Modified December 27, 2012 at 6:17:07 AM PST by RaphaniacZX

Chosen solution

Most suggestion apply to Flash 11.3 and later and thus can be tried with Flash 11.4

You can check for problems caused by recent Flash updates and try these:

disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed

Firefox users with Flash 11.3 and RealPlayer installed have reported that Flash videos or games on sites like Facebook or YouTube may appear, black, white or grey and never play. This can be fixed by updating to the latest version of RealPlayer.
Table of Contents

Flash 11.3 doesn't load video in Firefox
Firefox users with Flash 11.3 and RealPlayer installed have reported that Flash videos or games on sites like Facebook or YouTube may appear, black, white or grey and never play. This can be fixed by updating to the latest version of RealPlayer.
Table of Contents
Solution 1: If you have RealPlayer installed - update it
Solution 2: Downgrade Flash
https://support.mozilla.org/en-US/kb/flash-113-doesnt-load-video-firefox

Helpful Reply

Thanks for the reply, but I think you didn't read what I wrote.
I'm using Flash 11.4, not 11.3, and I don't got crash issues,
I got performance issues.
Please take the time to read the details before posting something just like that.

Thanks for the reply, but I think you didn't read what I wrote.
I'm using Flash '''11.4''', not ''11.3'', and I don't got ''crash issues'',
I got '''performance issues'''.
Please take the time to read the details before posting something just like that.

Most suggestion apply to Flash 11.3 and later and thus can be tried with Flash 11.4
You can check for problems caused by recent Flash updates and try these:
*disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed
*disable protected mode in Flash 11.3 and later
*disable hardware acceleration in the Flash plugin
*http://kb.mozillazine.org/Flash#Flash_Player_11.3_Protected_Mode_-_Windows

Helpful Reply

THANK YOU SO MUCH.
I turned off the hardware acceleration/protected mode just as the page cited and now my flash content is working back again flawlessly, thanks a lot for the help.
Hope it helps more people.

'''THANK YOU SO MUCH'''.
I turned off the hardware acceleration/protected mode just as the page cited and now my flash content is working back again flawlessly, '''thanks a lot for the help'''.
Hope it helps more people.

Hi,
My flash player is showing all the symptoms described in this article: http://kb.mozillazine.org/Flash#Flash_Player_11.3_Protected_Mode_-_Windows. I disabled the hardware acceleration and turned off protected mode. Since that didn´t work, I downgraded my flash player following the instructions in https://support.mozilla.org/en-US/kb/flash-113-doesnt-load-video-firefox. Still no change. Video playback and flash games are still laggy and choppy. My laptop is fairly new and the specs are all pretty decent. So I don´t think that´s the problem.
Any suggestions?
Thanks in advance.